According to the procedure they normally followed, when a pilot made a turn, he’d call it over the radio—“turning in,” “turning off,” “turning downwind,” “turning base.” Most of these calls were for the information of the other pilots, to let everyone know where he was. But the “turning base” call was more serious. That call let the safety observer in the tower know he was about to approach the target. When the observer heard that, he would be watching the aircraft ahead of the caller making his firing pass, which meant he was also ready to hear the next pilot’s turning-in hot call. Then he would give the pilot, or deny him, clearance to fire. For instance, if another airplane was in the way, he would say, “Make a dry pass” or “You’re not cleared.” And then the pilot would break off his attack, fly through level, and resume the correct spacing.

At Wheelus was a nuclear target circle, next to the conventional bomb circle and strafe targets. This circle had a long run-in bulldozed in the desert that served as a guideline about where to fly when the fighters were in the strafe pattern. On the run-in line was a smaller bulldozed line, more like a short streak across it, that was located 13,000 feet out from the nuclear bomb bull’s-eye. This mark was exactly the right place to start the turn to base leg to set up a pass at the strafe target. Normally, pilots making the gunnery run would turn base over that same streak. On this day, though, the pilot (number two) ahead of Horner got lost. Instead of turning base over the bulldozed lines in the desert, he kept flying away from the target and the proper place to begin his base leg turn.

Horner, meanwhile, was waiting for him to call base, as he himself was closing in on the base turning point. Finally, the call came, “Turning base.” Meaning: Horner was looking for him on base to his left front, expecting him to be moving toward the final attack roll-in point. Of course, he wasn’t anywhere near there; he was in front of Horner, far from the base leg and the target.